Bluebunch Wheatgrass Response to Spring Defoliation on Foothill Rangeland |
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| Institution: | 1. Assistant Research Professor, Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717;2. Professor, Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717;3. County Agent, Montana State University Extension Service, Philipsburg, MT 59858;4. Research Associate, Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717;1. Executive Director, Sustainable Rangelands Roundtable and Research Scientist, Department of Ecosystem Science and Management, University of Wyoming, Fort Collins, CO 80526, USA;2. Director, Fiscal and Business Operations, School for the Future of Innovation in Society, and Managing Director, Consortium for Science, Policy and Outcomes, Arizona State University, Tempe, AZ 85287, USA;3. Associate Director, Wyoming Agricultural Experiment Station, Director, James C. Hageman Sustainable Agriculture Research and Extension Center, Director, Powell Research and Extension Center, University of Wyoming, Laramie, WY 82071, USA;4. Center Manager, Center for Land Stewardship, Noble Foundation, Ardmore, OK 73401, USA;1. Research Ecologist (Postdoctoral), USDA–Agricultural Research Service, Eastern Oregon Agricultural Research Center, Burns, OR 97720, USA;2. Professor, Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT 84602, USA;3. Associate Professor, Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT 84602, USA;4. Associate Professor, Geography Department, Brigham Young University, Provo, UT 84602, USA;5. Professor, Department of Rangeland Ecology and Management, University of Idaho, Moscow, ID 83844, USA |
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| Abstract: | Spring elk grazing may reduce forage availability for wildlife or livestock in summer and may harm forage resources on foothill rangeland. We quantified bluebunch wheatgrass (Pseudoroegneria spicata Pursh] A. Love) response to spring defoliation on foothill rangeland in southwestern Montana. Two experiments were conducted simultaneously on a foothill grassland site and a foothill sagebrush steppe site. Bluebunch wheatgrass plants (n = 800) were selected and excluded from wild and domestic ungulates. Clipping treatments were applied in either early spring (mid- to late April) or late spring (mid- to late May), and plants were clipped to 1 of 3 residual heights (3, 6, or 9 cm) for 1, 2, or 3 successive years. Unclipped plants served as controls. Plant response was measured in late June and late July on both sites. April clipping for 3 successive years did not adversely affect bluebunch wheatgrass in June or July (P > 0.05) at either site. On foothill grassland, May defoliation to 3 cm for 2 consecutive years reduced leaf height (P = 0.04) in July. May defoliation for 3 successive years to 3 or 6 cm reduced plant yield (P < 0.05) and leaf height (P < 0.05) in June, and May defoliation for 3 successive years to 3 cm reduced leaf height (P = 0.02) in July. On foothill sagebrush steppe, 3 successive years of May defoliation to ≤ 9-cm stubble heights decreased leaf height in June (P < 0.05). We conclude that foothill rangelands where bluebunch wheatgrass receives moderate or light defoliation (6–9-cm residual stubble heights) in mid- to late May should be limited to no more than 2 successive years of mid- to late May grazing, whereas sites that receive heavy to severe defoliation (≤ 3-cm residual stubble heights) in mid- to late May should not be grazed for 2 successive years during mid- to late May. |
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